HHC is probably illegal in Iowa. This is one of the most restrictive states regarding marijuana and hemp laws. While there is no specific mention of HHC, the Iowa State Code considers CBD and delta 8 illegal, so it would be correct to infer that HHC is also banned.
Most US states don’t have any laws covering HHC. Despite this compound being around for decades, it seems lawmakers haven’t heard of it yet. Because of this, HHC is legal in most but not all US states. Here’s a snapshot of the current state of HHC legality in the United States.